Clinical evaluation of heart contractility is a crucial stake in cardiology, for detecting a number of cardiac pathologies such as dilated or hypertrophic cardiomyopathy, myocardial infarction, ischemia, etc.
Heart contractility is usually evaluated by assessing the End-Systolic Pressure-Volume Relationship (ESPVR), which normally requires a large number of invasive measurements on the patient, during several cardiac cycles. The ESPVR is a linear relation which is characterized in particular by its slope, the end-systolic elastance (Emax or Ees).
Non-invasive methods to assess ESPVR have been designed to avoid this drawback. For instance, WO-A-98/19594 describes such a non-invasive, single beat measurement method, wherein measurements of pressure, heart volume and heart beat are carried out (some of them such as pressure estimation being even invasive), which are then used to estimate the ESPVR based on statistic data.
However, this known method is still complex since it requires simultaneous use of a lot of measurement devices. Further, this method is based on several assumptions:                that the heart under examination follows the statistic laws used by the method,        that elastance is a linear function of time,        and that the volume-axis intercept of the Pressure-Volume diagram remains constant during a cardiac cycle.        
These assumptions may turn out to be erroneous in certain cases and thus result in a wrong estimate of the ESPVR.